Sensorless Control and Corrected Error Commutation of the Brushless DC Motor

Abstract

This paper presents a simple method for correcting the error of commutation windings for sensorless control of a brushless DC motor with a small inductance. Switching error analysis is performed based on the phase currents of the switched-off and switched-on phases. To correct the commutatiuon signals for the inverter, a speed-independent function is used, calculated from the back-EMF, by selecting its coefficients. The back-EMF is calculated for the system obtained by transformed a three-phase system to a two-phase one, which reduces the system dimension. An algorithm for start-up the motor with sensorless control based on the method of align and damping the rotor vibrations in a stable equilibrium position is proposed. The back-EMF is approximated by a function based on a piecewise linear function and an inscribed ellipse, for a more accurate description of the shape of the back-EMF. This approximation is used when simulation the motor. The simulation confirms the effectiveness of the proposed method for correcting the commutation error in the case of sensorless control of a low-power BLDC motor.